The middle of five children. His father was a police detective and his mother was a social worker. He earned a bachelor's degree from St. Vincent College in Latrobe, Pennsylvania, and went on to study in the M.F.A. program on a full scholarship at the Catholic University of America in Washington, D.C. Kelly appeared in numerous Off-Broadway and Off-Off-Broadway productions, primarily at the Public Theater and Second Stage. Coming from regional national theater, he was a member of the company of the Williamstown Theatre Festival, the Folger Theatre, Arena Stage, and the Actors Theatre of Louisville, among others.

He toured with the National Players, the oldest classical touring company in the United States. He played the role of Brick on Broadway opposite Kathleen Turner in "Cat on a Hot Tin Roof" and the role of Paul Verrall opposite Madeline Kahn in "Born Yesterday." In 2003 he appeared at the Mark Taper Theater Forum, playing the original role of Richard in Lisa Loomer's "Living Out."